Recently, there is increasing demand for exterior materials for electric and electronic products or automobiles having high functionality and high performance. In particular, with increasing emphasis on external appearances of molded resins, there is increasing demand for high gloss resin materials, which can exhibit pleasant texture and scratch resistance at the same time, and high heat resistant materials, which can be used together with a heat emitting device, such as a light emitting diode (LED).
Acrylic resins capable of exhibiting scratch resistance, particularly, polymethylmethacrylate (PMMA), exhibit excellent properties in terms of transparency, weather resistance, mechanical strength, surface gloss, adhesion, and the like. However, such acrylic resins have drawbacks of poor impact resistance and heat resistance. In order to secure scratch resistance and heat resistance at the same time, it has been attempted to increase the number of covalent bonds in the backbone through post modification after preparation of a polymethyl methacrylate copolymer having good scratch resistance. However, since this method is not suitable for mass production due to a long time for post-treatment and high production costs resulting from the post treatment, this method has been restrictively used in the art. Moreover, this method requires the post-treatment, thereby causing deterioration in mechanical properties of the resin.
In order to achieve properties including scratch resistance, high refractivity and high heat resistance while overcoming such problems, there is proposed a method in which a highly refractive monomer having a high index of refraction and exhibiting heat resistance is subjected to copolymerization in preparation of a PMMA copolymer resin. However, this method has restriction in improvement in the index of refraction or heat resistance of the copolymer prepared using the highly refractive monomer.